The development of the caudal ligaments of the mesonephros and of the gonads: a contribution to the development of the human gubernaculum (Hunteri).

The formation of the two caudal mesonephric folds is described. The plica uropelvina becomes the plica urogenitalis as soon as the paramesonephric (Müllerian) duct grows, and the plica inguinalis runs over the ridge of the umbilical artery to the ventral abdominal wall. Within the plica inguinalis the inguinal or caudal mesonephric ligament is formed directly subjacent to the coelomic epithelium. It interacts intensively with the mesenchyme sheath of the paramesonephric (Müllerian) duct in stage 21. It is separated by loose mesenchyme from the subjacent mesonephros and mesonephric (Wolffian) duct which therefore it does not pass beneath. In stage 23, and during the early fetal period, the caudal gonadal ligament is formed. It arises from the caudal pole of the gonads and proliferates in the space between the two genital ducts. Only the duct not destined to disappear associates with it. Therefore, in males the gubernaculum consists of the inguinal ligament of the mesonephros only. Its significance for the descent of the testis is discussed. In females the inguinal and the caudal gonadal ligaments fuse into a single strand and together form the gubernaculum.